Firing chamber seal

ABSTRACT

A combination projectile guide and firing chamber seal especially adapted for use in caseless cartridge firing weapons. The seal consists of a tubular member which is adapted to be attached to the breech end of a weapon barrel with a tubular portion projecting into the firing chamber in close spaced relation to the inner diameter wall thereof. The outer diameter of the seal has a series of annular pressure drop grooves which successively reduce the propellant gas pressure. The front end of the tube has an increased diameter conical counterbore adapted to guide a projectile to the main bore which is concentric with and has a diameter equal to the bore of the weapon barrel. The presence of a pressure differential caused by the annular grooves allows the front end of the seal to circumferentially expand within the firing chamber, thereby further reducing the gas flow.

United States Patent [72] Inventors Duane A. Somers Port Clinton; Edward S. Daniels, Port Clinton; William E. Lahey, Oakharbor, all oi, Ohio [2]] Appl. No. 821,639 [22] Filed May 5, 1969 [45] Patented Aug.3, 1971 [73] Assignec TRW lnc.

Cleveland, Ohio [54] FIRING CHAMBER SEAL 2 Claims,4 Drawing Figs.

[52] US. Cl 89/26, 42/395 [51] Int. Cl. F41c 21/00 [50] Field ofSearch 89/l7,26, l55, 156, 157,191, 192, 193;42/2, 15, 27, 39.5

[56] References Cited UNITED STATES PATENTS 2,416,287 2/1947 Coates et a]. 89/191 X 3,246,567 4/1966 Miller 89/191 3,302,523 2/1967 Langenhoven et a] 42/395 X 3,474,560 l0/l969 Ramsay 42/15 X FORElGN PATENTS 135,475 l92l Great Britain 89/26 Primary Examiner-Benjamin A. Borchelt Assistant Examiner-Stephen C, Bentley Attorney-Hill, Sherman, Meroni, Gross & Simpson ABSTRACT: A combination projectile guide and firing chamber seal especially adapted for use in caseless cartridge firing weapons. The seal consists of a tubular member which is adapted to be attached to the breech end of a weapon barrel with a tubular portion projecting into the firing chamber in close spaced relation to the inner diameter wall thereof. The outer diameter of the seal has a series of annular pressure drop grooves which successively reduce the propellant gas pressure. The front end of the tube has an increased diameter conical counterbore adapted to guide a projectile to the main bore which is concentric with and has a diameter equal to the bore of the weapon barrel. The presence of a pressure differential caused by the annular grooves allows the front end of the seal to circumferentially expand within the firing chamber, thereby further reducing the gas flow.

FIRING CHAMBER SEAL BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to weapons and more particularly to a firing chamber seal and projectile guide.

2. Prior Art Normal ammunition cartridges which have the propellant mix encased in a metal casing provide sealing or obturation of the firing chamber through circumferential expansion of the cartridge case. Recently caseless cartridges have been developed which are constructed either entirely of propellant or which have consumable cases unable to provide the necessary obturation.

Weapons designed to fire such caseless cartridges may require obturation at the front end of the firing chamber. In such weapons, the firing chamber may be defined by a separate mechanism which is backed against the breech end of the barrel.

Further, because the projectile is not always properly aligned with the bore of the weapon barrel, it is desirable to have a projectile guide located adjacent. the breech end of the barrel which will realign a fired projectile prior to its entrance into the barrel bore. It has been suggested that front end obturation of the firing chamber can be obtained by a cylindrical extension of the barrel which projects into the firing chamber and which will be circumferentially expanded into tight sealing engagement with the inner diameter of the firing chamber by the pressure of the propellant gases. Such solutions have required the use of relatively thin-walled cylindrical projections which can be damaged by misaligned projectiles abutting against them and which are subject to fatigue due to continued expansion and contraction during operation of the weapon.

SUMMARY OF THE INVENTION This invention overcomes the disadvantages of the prior art and provides for a new and improved firing chamber obturator and projectile guide. The invention consists, in a preferred embodiment, of a tubular unit having an out-turned flange adjacent one end which is adapted to be received in a counterbore in the breech end of a weapon barrel concentric with the bore thereof. The tubular portion of the combination guide and seal projects into the firing chamber and has a central bore of equal diameter to and concentric with the weapon barrel bore. The central bore has a tapering increased diameter counterbore in it extending inwardly from the end opposite the barrel end. The tubular portion is relatively thick-walled and has an outer diameter slightly less than the inner diameter of the firing chamber so that it projects into the firing chamber in close spaced relation to the inner diameter thereof. A series of annular grooves is formed into the outside diameter of the tubular portion.

As the propellant of the cartridge burns in the firing chamber, high pressure propellant gas will flow around the outside of the seal in the narrow annular space between the outside diameter of the front end of the seal and the inside diameter of the firing chamber. As the gas flows through this small orifice, it will come in contact with the succession of annular grooves. The gas expands in each groove resulting in a series of pressure drops. By the time the gas reaches the end of the seal adjacent the barrel end, it is at a low pressure and the firing chamber is effectively sealed. As the gas pressure in the chamber increases from the burning propellant, the front end of the seal remote from the barrel end expands slightly due to the pressure differential between the inside and outside wall of the seal. This expansion decreases the orifice area between the outer diameter of the seal and the inner diameter of the firing chamber, thus further restricting the gas flow around the seal.

It is therefore an object of this invention to provide an improved firing chamber seal.

It is a further object of this invention to provide a combination firing chamber seal and projectile guide which is sufficiently thick-walled in cross section to resist damage and metal fatigue during operation of the weapon in which it is installed.

It is yet another object of this invention to provide a combination firing chamber front end obturator and projectile guide which has a tubular portion having its outer diameter in close spaced relation to the inner diameter of 'the firing chamber and which has an outer diameter configuration adapted to present a series of pressure drop areas which successively reduce the propellant gas pressure to effectively seal the front end of the firing chamber.

It is yet another and more important object of this invention to provide a combination weapon chamber obturator and projectile guide which has a tubular portion with an out-turned flange adjacent one end adapted to be attached to the breech end of a weapon barrel, the tubular portion having a relatively thick cross section and a series of annular grooves in the outer diameter thereof, a counterbore in the end remote from the flanged end adapted to act as a projectile guide to guide a projectile into alignment with the weapon barrel bore, the grooves adapted to act as a series of pressure drop zones to adequately seal the front end of the weapons firing chamber.

Other and further objects of this invention will be apparent to those skilled in this art from the following detailed description of the annexed sheets of drawings which, by way of a preferred embodiment of the invention, illustrate one example of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of the combination projectile guide and seal of this invention.

FIG. 2 is an end plan viewof the projectile guide and seal of FIG. 1.

FIG. 3 is a fragmentary cross-sectional view of the combination projectile guide and seal of FIG. 1 installed in a weapon.

FIG. 4 is a view similar to FIG. 3 illustrating the effect of high-pressure propellent gases on the seal.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates the combination seal and projectile guide 10 in cross section. The combination consists of a tubular body 11 having an out-tumed flange 12 at one end thereof. The body 11 has an axial bore 13 therethrough which has an increasing diameter counterbore 14 at the end 15 remote from the flange 12.

The body 11 has a substantially thick wall which tapers slightly at the end 15 due to the counterbore 14. The outer diameter 16 of the tubular body 11 has a series of annular axially spaced-apart grooves 17 therein. The grooves 17 are illustrated as extending into the wall of the tubular body 11 a proximately half its thickness and as being spaced between the end of the counterbore and the flange. However, it is to be understood that the number, depth and placing of the grooves 17 is for purposes of illustration only and that this may vary depending upon the size of the weapon in which the combination 10 is used.

FIG. 3 illustrates a fragmentary cross-sectional view of a simplified weapon employing the combination projectile guide and seal 10. The weapon is illustrated as consisting of a barrel 20 having a bore 21 therethrough. The weapon barrel 20 has an end 22 against which a sliding sleeve firing chamber bottoms. The firing chamber consists of a cylindrical axially movable sleeve 23 which has a firing chamber bore 24 therein. The firing chamber 24 is coaxial with the bore of the barrel 21 but has a larger diameter. A portion of a caseless cartridge 25 is illustrated. The cartridge 25 is of the telescope type which has a molded propellant body with a projectile telescopically received therein. Igniting the cartridge will force the projectile out of the cartridge 25 in the direction of the barrel 20.

Because the projectile is attached to a consumable case cartridge rather than anchored to a heavy case cartridge, it is possible for the projectile to become misaligned in the cartridge. Further, because of the relative ease with which such caseless cartridges can be chipped on their exterior diameter, it is possible for the cartridge to be misaligned in the firing chamber with respect to the bore 21 of the barrel. For this reason, it is necessary to realign the projectile after it has begun to emerge from the cartridge.

Firing of the cartridge will fill the firing chamber with highpressure propellant gases which drive the projectile through the weapon bore. If not otherwise stopped, these gases will escape at the interface 26 between the end 22 of the barrel and the front end 27 of the sleeve 23. Due to the velocity of the propellant gases, leakage at the interface 26 can cause extensive erosion of weapon parts. In addition, any leakage of propellant pressure decreases the speed of the projectile and reduces the effectiveness of the weapon.

The combination seal and projectile guide is provided to compensate for these difficulties. The combination 10 is illustrated as being received in a counterbore 30 in the end 22 of the barrel 20. The counterbore 30 is concentric with the barrel bore 21 and has axial and radial dimensions equal to the axial and radial dimensions of the flange 12 so that the combination 10 can be snugly received in the counterbore with the end 31 of the flange 12 lying flush with the end 22 of the barrel. Although the combination 10 is illustrated as being received in a counterbore in the weapon barrel, it is to be understood that other methods of attaching the combination to the barrel may be used including devices such as locking collars which will more firmly anchor the combination to the barrel.

The flange 12 preferably has an outer diameter which is greater than the inner diameter of the firing chamber bore 24 while the tubular body 11 has an outer diameter which is slightly less than the inner diameter of the firing chamber. This will provide an annular gap 35 between the outer diameter of the tubular portion 11 and the inner diameter of the firing chamber. The gap 35 is kept minimal but allows free clearance of the sleeve 23 when reciprocating back and forth around the tubular body portion 11 which projects into the firing chamber. The bore 13 of the combination 10 is coaxial with and of equal diameter to the bore 21 of the barrel and provides an extension thereof. The tapering counterbore 14 then functions as a projectile guide redirecting any misaligned projectiles as they exit from the cartridge 25 into alignment with the nontapered portion of the bore 13 and therefore with the bore 21 of the weapon barrel. Because the wall of the tubular body 11 is substantially thick, the combination 10 is able to adequately function as a projectile guide and will not be damaged by contact with a misaligned projectile.

As the cartridge is fired, the pressure gases build up and begin to flow through the annular gap 35 around the outside of the seal. As the gas flows through the small orifice 36 at the front end of the tubular body 11 it comes in contact with a series of annular grooves 17. The gas expands in each groove resulting in a pressure drop in that groove. The thus-expanded gas will then flow around the ribs 37 separating each groove and into the next groove where it will again expand resulting in a further pressure drop. By the time the gas reaches the end of the sea] at the face 31 of the flange 12, it is at a low pressure and the firing chamber 24 is in effect sealed. In addition, as is illustrated in FIG. 4, due to the reduction in wall thickness at the end 15 caused by the counterbore 14, that portion of the tubular body 11 encounters a degree of circumferential expansion. The expansion is caused by the pressure difference between the inner and outer diameter faces of the tubular body 11. As the end 15 circumferentially expands, the annular gap 35 decreases thereby reducing the orifice. This further restricts the gas flow around the seal.

Preferably the end 15 will expand to a point where the gap 35 is almost nonexistent, but the body of the combination is not touching the inner diameter of the firing chamber. Therefore, even with the weapon operating at the fastest possible rate, the combination will not rub against the sleeve. Of

course, due to the substantial thickness of the tubular body 11, as soon as the gas pressure recedes, the end 15 will contract to its original shape.

Because the combination projectile guide and seal is formed as an independent part, it is easily removable in case of wear or damage. In addition, because of its thick wall structure, it is not subject to flex fatigue. Although the combination does not act as an absolute seal, because of the extremely short period of time during which the high propellant gas pressures exist, the combination will adequately seal the front end of the firing chamber.

It can therefore be seen from the above that our invention provides a combination projectile guide and firing chamber seal which is substantially thick-walled to align fired projectiles with the bore of a barrel prior to their entering the barrel and which seals the firing chamber by creating a combination of a small orifice and a succession of pressure drop areas.

We claim as our invention:

1. A combination projectile guide and firing chamber seal for use in cartridge firing weapons which have an annular firing chamber adjacent an end of the weapon barrel and a bore through the barrel communicating to the firing chamber with an interface between the chamber and the barrel end which comprises: a counterbore in the said end of the said barrel concentric with the said bore, a seal member having a tubular portion with an out-turned flange adjacent one end thereof, the said flange inserted in the said counterbore to attach the said seal member to the said barrel end, the said flange seating flush with the said end of the said barrel in the said counterbore, the tubular portion projecting from the said flange into the said firing chamber, the said tubular portion having a bore therethrough concentric with the bore of the barrel and having a constant diameter substantially equal to the barrel diameter for the major portion of its length therefrom from the flanged end, a counterbore in the nonflanged end of the said tubular portion concentric with the bore of the said major portion, the said counterbore providing a decreased thickness in the wall of the said tubular member at the nonflanged end thereof, said decreased thickness portion expandable circumferentially in response to increased pressure interiorly of the said firing chamber, the said firing chamber having a diameter slightly greater than the outer diameter of the said tubular portion, a small gap between the diameter wall of the said firing chamber and the outer diameter of the said tubular portion, a plurality of gas trap grooves around the outer diameter of the said tubular portion intermediate the said counterbored end and the said flanged end, and the said expansible portion effective to decrease the said gap in the area of the said flanged end in response to the said pressure increase.

2. The combination of claim 1 wherein a front end of the said firing chamber abuts a portion of the said flange and a portion of the said barrel end at the interface. 

1. A combination projectile guide and firing chamber seal for use in cartridge firing weapons which have an annular firing chamber adjacent an end of the weapon barrel and a bore through the barrel communicating to the firing chamber with an interface between the chamber and the barrel end which comprises: a counterbore in the said end of the said barrel concentric with the said bore, a seal member having a tubular portion with an out-turned flange adjacent one end thereof, the said flange inserted in the said counterbore to attach the said seal member to the said barrel end, the said flange seating flush with the said end of the said barrel in the said counterbore, the tubular portion projecting from the said flange into the said firing chamber, the said tubular portion having a bore therethrough concentric with the bore of the barrel and having a constant diameter substantially equal to the barrel diameter for the major portion of its length therefrom from the flanged end, a counterbore in the nonflanged end of the said tubular portion concentric with the bore of the said major portion, the said counterbore providing a decreased thickness in the wall of the said tubular member at the nonflanged end thereof, said decreased thiCkness portion expandable circumferentially in response to increased pressure interiorly of the said firing chamber, the said firing chamber having a diameter slightly greater than the outer diameter of the said tubular portion, a small gap between the diameter wall of the said firing chamber and the outer diameter of the said tubular portion, a plurality of gas trap grooves around the outer diameter of the said tubular portion intermediate the said counterbored end and the said flanged end, and the said expansible portion effective to decrease the said gap in the area of the said flanged end in response to the said pressure increase.
 2. The combination of claim 1 wherein a front end of the said firing chamber abuts a portion of the said flange and a portion of the said barrel end at the interface. 